From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D92E9C001E0 for ; Mon, 23 Oct 2023 07:09:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229862AbjJWHJr (ORCPT ); Mon, 23 Oct 2023 03:09:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50122 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229450AbjJWHJp (ORCPT ); Mon, 23 Oct 2023 03:09:45 -0400 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C30BB8F for ; Mon, 23 Oct 2023 00:09:41 -0700 (PDT) Received: from kwepemm000013.china.huawei.com (unknown [172.30.72.56]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4SDR6J1gtnzMmC4; Mon, 23 Oct 2023 15:05:28 +0800 (CST) Received: from [10.174.178.46] (10.174.178.46) by kwepemm000013.china.huawei.com (7.193.23.81) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.31; Mon, 23 Oct 2023 15:09:38 +0800 Subject: Re: [PATCH v2] ubi: gluebi: Fix NULL pointer dereference caused by ftl notifier To: Richard Weinberger CC: ZhaoLong Wang , Miquel Raynal , Vignesh Raghavendra , dpervushin , Artem Bityutskiy , linux-mtd , linux-kernel , yi zhang , yangerkun References: <20231018121618.778385-1-wangzhaolong1@huawei.com> <1381458025.20897.1697747248632.JavaMail.zimbra@nod.at> <891e554b-c133-6378-3a65-836fc9147e54@huawei.com> <441107100.23734.1697904580252.JavaMail.zimbra@nod.at> From: Zhihao Cheng Message-ID: <93b2d5ab-e36c-be08-7343-ef4ca16f991d@huawei.com> Date: Mon, 23 Oct 2023 15:09:26 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <441107100.23734.1697904580252.JavaMail.zimbra@nod.at> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.178.46] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To kwepemm000013.china.huawei.com (7.193.23.81) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2023/10/22 0:09, Richard Weinberger 写道: > ----- Ursprüngliche Mail ----- >> Von: "chengzhihao1" >>>> Such a modification currently works because the mutex "mtd_table_mutex" >>>> is held on all necessary paths, including the ftl_add_mtd() call path, >>>> open and close paths. Therefore, many race condition can be avoided. >>> >>> I see the problem, but I'm not really satisfied by the solution. >>> Adding this hack to gluebi_read() is not nice at all. >> >> Yes, it's jsut a workaround. At the begining, I prefer that increasing >> volume refcnt (by ubi_open_volume) in gluebi_create and releasing volume >> refcnt in gluebi_remove. It looks more reasonable that holding a refcnt >> of UBI volume when gluebi is alive. After looking through the code, the >> creation/destroying of gluebi is triggered by volume >> actions(UBI_VOLUME_ADDED/UBI_VOLUME_REMOVED), which means that: >> 1. gluebi_remove is depended on UBI_VOLUME_REMOVED(triggered by >> ubi_remove_volume) >> 2. ubi_remove_volume won't be executed until the refcnt of volume >> becomes 0(released by gluebi_remove) >> >> If we add new ioctls to control creation/destroying of gluebi, then >> gluebi mtd won't be automatically created when UBI volume is added. I'm >> not certain whether this change will effect existing startup process >> that depends on gluebi. > > Let's take a stack back. The sole purpose of gluebi is providing > a way to run JFFS2 on top of UBI. Is it possible that someone runs ext4 on mtdblock based on gluebi, for the advantage of wear-leveling? > IMHO there is no need to run an FTL on top of UBI or even mtdblock. > This kind of stacking does not make sense. > > So, I'd go so far and propose the following: > diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c > index ff18636e08897..b362a64411ebd 100644 > --- a/drivers/mtd/mtd_blkdevs.c > +++ b/drivers/mtd/mtd_blkdevs.c > @@ -463,7 +463,7 @@ static void blktrans_notify_add(struct mtd_info *mtd) > { > struct mtd_blktrans_ops *tr; > > - if (mtd->type == MTD_ABSENT) > + if (mtd->type == MTD_ABSENT || mtd->type == MTD_UBIVOLUME) > return; > > list_for_each_entry(tr, &blktrans_majors, list) > > IOW, no mtdblock (hence, also no FTLs) on top of gluebi. > > What do you guys think? > > Thanks, > //richard > > . >